No glass at my coop, except for the exterior grade door on the south wall, a Restore buy at $8.00 years ago.
Cover openings with hardware cloth, very well secured, and with big roof overhangs, it's good. if not, the hinged shutter from the top works very well.
Here in winter we cover tow of the windows with sheet vinyl, and the run walls also, leaving one to two feet open at the top for ventilation. Again, with roof overhangs, little or no snow will blow inside.
Closing everything up is very bad for the birds, they need good ventilation all year. It's making it overhead, not at roost level, for very cold weather.
Mary